Orbital Sciences Corporation : ORBITAL SET TO LAUNCH COTS DEMONSTRATION MISSION TO INTERNATIONAL SPACE STATION TOMORROW

-- Upcoming Mission Represents Final Milestone in the Development of Antares Launch Vehicle and Cygnus Cargo Logistics Spacecraft --

(Dulles, VA 17 September 2013) - Orbital Sciences Corporation
ORB, +6.92%
one of the world's leading space technology companies, today announced it is prepared to launch its Antares rocket carrying the company's new Cygnus cargo spacecraft to the International Space Station (ISS) tomorrow morning. The launch is currently planned to take place on Wednesday, September 18, with lift-off scheduled at 10:50 a.m. (EDT) from the Mid-Atlantic Regional Spaceport (MARS) at NASA's Wallops Flight Facility on Wallops Island, VA. Antares will launch Cygnus into a targeted orbit of 245 x 300 kilometers, inclined at 51.6 degrees to the equator. Following in-orbit activation shortly after launch, Cygnus will carry out a series of tests and maneuvers over a four-day period to demonstrate its readiness to rendezvous and berth with the station, now planned for Sunday, September 22.

"Antares is the largest and most complex rocket Orbital has ever produced," said Mr. David W. Thompson, Orbital's President and Chief Executive Officer. "After its flawless inaugural flight in April, we have been actively preparing for this next critical, much-anticipated milestone. Likewise, Cygnus is one of the most sophisticated spacecraft Orbital has developed and built. As an integral part of the Space Station program, it meets NASA's requirements for a human-rated level of safety. Our engineering and operations teams are very excited to be on the threshold of launching and conducting this mission, which they have been working toward for the last five years."

The goal of the mission is to demonstrate the capability of Orbital's cargo transportation system to reliably deliver cargo to the ISS, which will lead to regularly scheduled missions beginning as early as December. This demonstration flight is the final milestone in Orbital's Commercial Orbital Transportation Services (COTS) joint research and development initiative with NASA. Under the COTS program, which began in 2008, NASA and Orbital developed Cygnus, which meets the stringent human-rated safety requirements for ISS operations. Orbital also privately developed the Antares launch vehicle to provide low-cost, reliable access to space for medium-class payloads. Together, these elements are being used for the COTS flight demonstration of Orbital's commercial cargo supply capability to the ISS.

Pending the successful completion of the COTS program, Orbital will begin regularly scheduled cargo delivery missions to the ISS under its $1.9 billion Commercial Resupply Services (CRS) contract with NASA. Under the CRS contract, Orbital will deliver approximately 20,000 kilograms of net cargo to the ISS over eight missions through 2016. For these missions, NASA will manifest a variety of essential items based on ISS program needs, including food, clothing, crew supplies, spare parts and equipment, and scientific experiments.

About Antares

The Antares medium-class launch vehicle will provide a major increase in the payload launch capability that Orbital can provide to NASA, the U.S. Air Force and commercial customers. The Antares rocket will launch spacecraft weighing up to 14,000 lbs. into low-Earth orbit, as well as lighter-weight payloads into higher-energy orbits. Orbital's newest launcher is currently on-ramped to both the NASA Launch Services-2 and the U.S. Air Force's Orbital/Suborbital Program-3 contracts, enabling the two largest U.S. government space launch customers to order Antares for "right-size and right-price" launch services for medium-class spacecraft. For more information on Antares, visit http://www.orbital.com/SpaceLaunch/Antares/.

About Cygnus

Orbital developed the Cygnus cargo spacecraft as part of its COTS joint research and development initiative with NASA. Cygnus consists of a common Service Module (SM) and a Pressurized Cargo Module (PCM). The SM incorporates avionics, power and propulsion systems already successfully flown aboard dozens of Orbital's LEOStar(TM) and GEOStar(TM) satellite products. The PCM, designed and built by Thales Alenia Space under a subcontract from Orbital, is based on the Multi-Purpose Logistics Module (MPLM) used with the Space Shuttle. For more information on Cygnus, visit http://www.orbital.com/NewsInfo/Publications/Cygnus_fact.pdf

About Orbital

Orbital develops and manufactures small- and medium-class rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-Earth orbit, geosynchronous-Earth orbit and planetary exploration spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also provides satellite subsystems and space-related technical services to U.S. Government agencies and laboratories. More information about Orbital can be found at http://www.orbital.com. Follow the company on Twitter @OrbitalSciences.

# # #

Contact:

Barron Beneski (703) 406-5528

Public and Investor Relations

Orbital Sciences Corporation

Beneski.barron@orbital.com

This announcement is distributed by Thomson Reuters on behalf of Thomson Reuters clients.

The owner of this announcement warrants that:

(i) the releases contained herein are protected by copyright and other applicable laws; and

(ii) they are solely responsible for the content, accuracy and originality of the

Intraday Data provided by SIX Financial Information and subject to terms of use.
Historical and current end-of-day data provided by SIX Financial Information. Intraday data
delayed per exchange requirements. S&P/Dow Jones Indices (SM) from Dow Jones & Company, Inc.
All quotes are in local exchange time. Real time last sale data provided by NASDAQ. More
information on NASDAQ traded symbols and their current financial status. Intraday
data delayed 15 minutes for Nasdaq, and 20 minutes for other exchanges. S&P/Dow Jones Indices (SM)
from Dow Jones & Company, Inc. SEHK intraday data is provided by SIX Financial Information and is
at least 60-minutes delayed. All quotes are in local exchange time.